How can wearable biosensors collect sweat without exercise?
Sweat has long been considered a valuable medium for real-time health monitoring, as it carries a rich source of molecular-level physiological information. However, its passive and activity-dependent secretion has posed a fundamental barrier to broader applications. In a new study published in National Science Review, He et. al present a fabric-based electrochemical biosensing system that enables autonomous sweat collection and molecular analysis across varied scenarios and user groups.
Triggering sweat, effortlessly
At the heart of this system lies a low-current iontophoresis module embedded in a breathable textile. It uses a skin-interfaced stabilized hydrogel (SSIH) electrode to deliver a mild current that activates sweat glands in a controlled and painless manner. This hydrogel ensures tight contact with the skin, enabling effective ionic delivery while minimizing discomfort and signal loss.
“We designed the interface to be soft, conformal, and electrically stable over time,” explains Prof. Sisi He, the corresponding authors of the study. “For efficient agonist delivery, the electrode also needed to achieve a delicate balance among drug transport efficiency, mechanical compliance with skin, biocompatibility, and long-term operational stability. These properties allow us to stimulate local sweating without relying on user movement or heat, which greatly broadens the scenarios where sweat biosensing can be applied.”
In trials with human volunteers, the sweat induction module reliably triggered localized perspiration within minutes using a current as low as 75 microamperes. This is significantly lower than the milliampere-level currents typically required by conventional iontophoresis systems. The amount of sweat induced was sufficient to activate downstream sensing modules. The stimulation caused no skin irritation or discomfort, even after repeated use.
From sweat droplets to biochemical data
Once sweat is induced, it flows through a hydrophilic layer toward biosensing fibers integrated into the textile. These fiber sensors, constructed with coaxial carbon nanotube electrodes, are modified with enzymes or conductive materials that enable the detection of multiple biomarkers, including glucose, lactate, uric acid, and pH. Moreover, to improve the long-term stability of the redox interface used for enzymatic signal transduction, the researchers introduced a nickel hexacyanoferrate (NiHCF) coating to reinforce the Prussian Blue layer. As a member of the Prussian Blue Analogue (PBA) family, NiHCF offers superior electrochemical stability compared to conventional Prussian Blue, which is prone to structural degradation and signal loss under repeated operation in physiological conditions. This modification enabled the sensors to deliver stable and repeatable signals during continuous monitoring for over 6 hours.
Toward autonomous health sensing in everyday life
To evaluate the system’s usability beyond the lab, the team seamlessly integrated the sweat stimulation and sensing modules into everyday clothing. The soft textile interface conformed comfortably to body areas such as the forearm and upper back, enabling long-term monitoring during common daily activities such as sitting at a desk, reading, or even sleeping. “Our goal was to enable physiological monitoring that blends naturally into people’s lives,” says Prof. Sisi He. “This platform operates autonomously and responds on demand, making it fundamentally more inclusive.”